Best solution for faster epub file created in InDesign for iPad

Explorer ,
May 21, 2021 May 21, 2021

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Hi

 

I am trying to optimise my InDesign epub file so it loads as quick as possible and I was interested to know if any of the following would speed up or slow down the process.

 

The epub file is a largely illustrated comic with drawings produced in Illustrator and text applied in InDesign

 

1. For the images on each page is it best to Place the Illustrator vector files on each page (this would be my default), copy and paste the vectors from Illustrator into InDesign (so they are embed and not linked) or save Illustrator vector pages as a rasterised file such as jpeg and Place the linked jpeg?

 

2. Similar to above but I have a few instances where I have used InDesign animation on text and a logo that fade/slide in, and also a series of paw prints that appear across the page (to simulate walking). Should I have the animated objects as placed illustrator vectors, vectors pasted in, or vectors converted to tranparent pngs and placed?

 

Thought somebody might know if the epub was created differently or more efficiently using one method over another.

 

Also do people usually export at 72ppi, 96ppi or 150ppi when the document is already set at the correct pixel size for the device?

 

Thanks

Dan

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EPUB, How to, Import and export, Publish online

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Adobe Community Professional ,
May 21, 2021 May 21, 2021

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It might be worth you having a look at CircularFLO, a useful facility for creating FXL ePubs from InDesign (it's Mac only): 

https://www.circularsoftware.com/apps/circularflo

 

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Guide ,
May 25, 2021 May 25, 2021

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Always export at 72ppi when you are working at the correct pixel size. So, if working with a iPad 2048x1536 document, export at 72 ppi. Anything over that value is waste of resources and your book will take a performance hit, as well as (in the worst case) be 3-4 times larger in file size.

 

[1] It depends. SVG is slow to render and animate compared to bitmap files, and depending on the complexity of the vector illustrations not necessarily smaller in terms of file size. Complex SVG files animated with javascript are a performance bottleneck - but test both versions: one with svg and one using PNG/jpg. 

 

In any case, my workflow is to NEVER depend on InDesign to rasterize graphics. I always use the "Use existing image for graphic objects" option in the Object Export options (epub and html tab) to ensure InDesign leaves my optimized assets well alone. InDesign is absolutely terrible at PNG image optimization.

 

Comic graphics generally (depending on the art style) may not require that many colours. I optimize mine with Color Quantizer http://x128.ho.ua/color-quantizer.html .

 

And check your final epub file for any empty PNG files. InDesign will generate those based on empty frames in your pages. These are saved as full-sized transparent PNG files, and must either be removed, or scaled down to ~64px versions. Realize that not doing this will cause these useless PNG files to gobble up video memory on a device like there is no tomorrow, and bog down performance again.

 

Also realize that if no tranparency is required, JPG may drastically reduce the file size of the epub. Backgrounds, for example, should be placed as JPG (unless these are simple lineart, which compresses better in PNG - but again, turn off that transparency for smaller PNG file sizes!)

 

PS did you know animated PNG files are supported in modern epub readers? For smaller animations which require full transparency very useful. They will not work in InDesign and must be placed via the method I mentioned above. But they do play on the Apple readers and Thorium on Windows. And in a browser.

 

PPS If working with SVG files: use a SVG optimizer to crunch file sizes. You can find several via Google. Then import again via above mentioned method.

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Explorer ,
May 25, 2021 May 25, 2021

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Thanks so much for the detailed response. I have started to optimise the images before importing using the 'Use existing image for graphic objects' as you suggested. Despite using InDesign for what must be 15 years now it's always been the print side for the most part.

 

I converted all vector illustrations to either jpeg or png at 100% size, whichever gave the smaller file size.

 

I've not tried importing an animated png into indesign but I have created animations from within InDesign for fade in, slide in etc, and they seem to work quite well.

 

I will experimant a little bit more but it's going well so far, I just need to crunch the file size down further. it has one video embed in it as it will be used offline so I will next optimize the video which should make a huge difference.

 

Thanks again.

 

 

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Adobe Community Professional ,
May 25, 2021 May 25, 2021

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@dw62059930  schrieb:

 

The epub file is a largely illustrated comic with drawings produced in Illustrator and text applied in InDesign

 

1. For the images on each page is it best to Place the Illustrator vector files on each page (this would be my default), copy and paste the vectors from Illustrator into InDesign (so they are embed and not linked) or save Illustrator vector pages as a rasterised file such as jpeg and Place the linked jpeg?

 

EPUBs dont use vector files, maybe SVG is possible. JPG is not good for Illu-drawings. Use PNG. Make an object style. Add replacement text for impaired people in a meta data field and use that field in the object style. Meta information can be edited in Bridge.

 

2. Similar to above but I have a few instances where I have used InDesign animation on text and a logo that fade/slide in, and also a series of paw prints that appear across the page (to simulate walking). Should I have the animated objects as placed illustrator vectors, vectors pasted in, or vectors converted to tranparent pngs and placed?

Avoid animiations. An EPUB is not a film.

 

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Explorer ,
May 25, 2021 May 25, 2021

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Thanks for coming back to me on this, based on what you've said i'll export my illustrations as both png and jpeg and check the quality side by side.

 

Point taken on the animations, I had so far only included it on the first page but will likely remove if it improves performance.

 

Thanks for your help.

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Guide ,
May 25, 2021 May 25, 2021

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quote

 

EPUBs dont use vector files, maybe SVG is possible. JPG is not good for Illu-drawings. Use PNG. Make an object style. Add replacement text for impaired people in a meta data field and use that field in the object style. Meta information can be edited in Bridge.

Please inform yourself about the epub 3 format before stating epub files do not support vector files.

https://www.w3.org/AudioVideo/ebook/

 

SVGs are entirely supported. 

 

Writing that JPG is an unsuitable format for illustrations is a too black-and-white statement: it depends. If no transparency is required, a high-quality jpg version generally wins easily in regards to file size compared to a PNG version. At the high resolution of a retina iPad screen it will look just fine.

 

But it depends on the content as well: a black and white illustration or one with few solid colours may compress better and at higher quality compared to a jpg version. 

 

And, of course, it may ultimately be a decision based on file size requirements. A full page sized retina background PNG image gobbles up file size rather quickly. 

 

SVG may wind up very small again depending on the content, and may be a better choice for static illustrations.

 

quote

Avoid animiations. An EPUB is not a film.

 

Interactive FXL epub 3 files support animation, audio and movie media files, javascript, CSS animations, ... Suffice to say, with the right reader supporting these things, animations fall well within the realms of possibility of the FXL epub 3 format.

 

If your target platform is the Apple readers (iOS and MacOSX) a wide range of animations are possible. As demonstrated by the interactive books available on the Apple ebook market. And the many animated interactive ebooks students of mine have designed in my classes.

 

That said, if the target platform should include users on Windows, Linux, and Android platforms, a FXL interactive epub file is probably the worst choice, and either an app/exectuable or web app/site is the best way to publish your work.

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Adobe Community Professional ,
May 26, 2021 May 26, 2021

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As long as it is not clear that EPUB3 is meant, I cannot recommend the use of animated graphics, nor SVG. I wrote above, maybe SVG. Many people do not have an EPUB3 reader, they can only use older versions. Therefore you have to be cautious. Many eader apps are on the field and you cannot determine which one is used. In some years the siuation might be different. 20 years ago no one would recommend the use of PNG, today a common file type.

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Adobe Community Professional ,
May 26, 2021 May 26, 2021

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JPG has a optimizing Algorythm which is not good for drawing and text, Therefore I cannot recommend the use for Illustrator files as Illustrator uses drawings and text. Transparency is not available for JPG and only very limitted for PNG and the transparency model of a PNG supports only alpha transparency. AI and PDF have a much wider spectrum of transparency functions.

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Explorer ,
May 26, 2021 May 26, 2021

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As it stands it's likely to only be designed for iPad iOS, but I can see this changing in the future.

I've run a few tests and i've not seen any noticable difference in the quality of jpeg vs png on my current illustrations, although I appreciate there will be to some extent and the differences may stand out more in drawings with different content/complexity. I was aware of the transparency aspect of pngs so there are a few instances when I wouldn't use jpeg.

 

I will look into saving illustrations as svg and seeing what that looks like as well, It's nice to learn something new and see what works best in certain situations.

 

I've been exporting as epub3 so far, but that's only because it's been the default export in InDesign, my tests have run ok on an old iPad, albeit too slow, but that's because the file is currently sitting at just under 60mb due to a video which needs optimising.

 

It is something that needs to be available offline so hosting on a website would not be possible most of the time which is why I opted for an epub over somthing published online. Initially it was going to be a document hosted on our server that sales reps/customers could download, but my director is now wanting to look at the possibility of adding it onto the Apple ebook store, so that's something else I need to investigate as i'm sure they have specific requirements such as maximum file size.

 

Thank you all for you help so far.

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